GEOLOGY AND MICROSTRUCTURAL STUDY OF PEMALI, BANGKA REGENCY, BANGKA BELITUNG ISLANDS

• Main Author: Vidi Faizal, Muhamad
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/44059
• Institution: Institut Teknologi Bandung

The rocks in Bangka Island are dominated by Paleozoic – Mesozoic rocks that had undergone polyphase deformation. Subduction of Paleo-Tethys followed by collision of Sibumasu and East Malaya (Indochina) Block contributed to polyphase deformation and regional metamorphism. Geological mapping in 1:25.000 scale combined with microstructure study using the concept of microtectonics by thin section observation have been conducted to explain the development of deformation and metamorphism that had occured in Bangka Island. The research area is located in Pemali, Merawang, and Sungailiat District, Bangka Regency, Bangka and Belitung Islands Province. The research area is located between 614000 – 623000 mT and 9783000 – 9793000 mU. Lithologic units comprise the Permian Schist Unit and Slate Unit, Lower Triassic Sandstone Unit, Upper Triassic Granites, and alluvial deposits. Schist and Slate Unit were formed in greenschist facies according to Barrovian metamorphism. Sandstone Unit was deposited in foreland basin and Granites Unit is S-type granites (biotite bearing granites). Thin section observation shows that stretching lineation and structures resulted from dynamic crystallisation are commonly found in Granites Unit, suggesting that the granites were also controlled by regional deformation. The regional deformation processes can be divided into four stages. The first deformation resulted in the formation foliated metamorphic rocks with NW – SE strike. The second deformation was related with thrust fault as shown by mylonite zone that indicate shear zones in brittle-ductile condition as the result of collision between Sibumasu and East Malaya Blocks in Early Trias. C-fabric (cisaillement) measurement shows NW – SE direction of shear zones. The third deformation occured between Upper Trias - Jura resulting NE – SW direction shear zone indicated by protomylonite zone. The fourth deformation took place during Tertiary and formed N-S right lateral strike slip fault.